Radio detector or amplification vacuum bulb



R. WEBSTER RADIO DETECTOR 0R AMPLI FICATION \fACUUM BULB April 20 1926. 1,581,992

Filed June 23, 1923 an alternating magnetic field Patented Apr. 20, 1926.

UNITED STATES PATENT OFFICE.

RONALD WEBSTER, OF EVANSTON. ILLINOIS, ASSIGNOR TO FANSTEEL PRODUCTS COMPANY, INC., 01 NORTH CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

RADIO DETECTOR OR AMPLIFICATION VACUUM BULB.

Application filed June 23, 1923. Serial No. 647,344.

T 0 all whom it may concern:

Be it known that I, RoNALn \Vicns'ruu, a citizen of the United States, and resident of Evanston, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Radio Detector or Amplification Vacuum Bulbs, of which the following is a full, clear, concise, and exact description, reference being had to the arcompanying drawings, forming a part of this specification.

My invention relates to radio detector or amplification vacuum hul'bs having therein a. tantalum element which may beheatcd 'for the purpose of absorbing the last trace of gases which are injurious to the successful operation of the vacuum tube.

The metal tantalum, when heated to a dull red temperature, has the quality of absorbing gases. It also has qualities which make it very advantageous for use as elements of a vacuum tube used for radio purposes. Tantalum may be used as a filament, and is particularly advantageous for that purpose in low voltage bulbs, because the tantalum has 2. hi her resistance than tungsten, which is usual y used as the filament, and, therefore, may be made with larger cross-sectional area for the same length than a tungsten filament. Tantalum may also be used as the material for the construction of the plate, and has been found satisfactory .for that a purpose as well as for the material of which the grid is made. I

When tantalum is used as the material of which the filament itself is made, no additional lead-in wires are necessary for heating the element to cause it to absorb the gas. The first use of the tube under its own heat will cause the tantalum filament to absorb the free gas. I prefer, however, to construct the plate of tantalum. Such a tantalum plate could be heated by providing the plate with two leads instead of the customary single lead and by means of the two terminals, sending a current through the plate suflicient to heat it to the necessary dull red to absorb the stray oxygen or other undesirable gas within the tube. As this is objectionable because of the expense of manufacture with an extra lead and terminal, I prefer to induce the necessary current in the grid by bringin the bulb into Figure 3 is a bottom view of the base,

showing the location of terminals thereon.

The construction m general is typical of detector bulbs now commercially manufactured. In the construction illustrated, the

filament 1, supported by a hook at the up r end of a supporting wire, 1' within the g ass vacuum tube 2, is provided with leadin wires 3 and 4 extending to the usual ter-' mina-l posts 5 and 6.

The element known as the grid is herein illustrated as a flattened helix 8, wound between spaced supporting wires 7-7, the former extending as lead wire 9 to its terminal post 10. The plate element 13 preferably consists of a pair of oppositely disposed sheets of tantalum beaded at their vertical margins to embrace supporting wires 14. The mid portions of these sheets are bent outwardly to space the plate from the grid, but the sheets are brought together adjacent the wires 14 to provide for the welding together of the sheets as indicated at 15. One of the plate supporting wires communicates with a lead-in wire extending to the terminal post 17.

In the use of my invention, the-tube is evacuated in the usual manner. It is then brought into a var ing magnetic field which may conveniently e obtained bythe'alternating flux from passing an alternating curratus in which it is important to absorb the last traces of free gas and contemplates any such apparatus in which one of the regularly supplied elements of the device is formed of tantalum for the purpose of gas absorption.

' I claim:

1. The method of eliminating end fractions of thegaseous contents of a vacuum tube which comprises constructing the plate element of tantalum and of a form afiording a closed electrical circuit, and placing the tube in an alternating current magnetic field which induces a current flow in said plate element suflicicnt to heat the latter for absorbing gases within the tube.

2. The method of eliminating a part of the gaseous contents of a vacuum tube which comprises mounting in the tube an element composed of tantalum, said element being of a form affording a closed electrical circuit, and subjecting said tantalum element to a magnetic field created 'in an external coil adjacent said tube, said tantalum element combining with the nitrogen and hydrogen contained in said tube. r

3. A vacuum tube for radio purposes com-- prising a plate in combination with the other usual element or elements, said plate being of a form affording a closed electrical circuit, and being composed; of tantalum adapted to be heated for absorbing gases Within the tube.

-l. The method of completing the exhaustion of a vacuum tube which comprises placing in the tube an element composed of tan- .talum, and heating such element for absorbing such gases as combine with heated tantalum including hydrogen and nitrogen.

In witness whereof, I hereunto subscribe by name'this 16th day of June, 1923.

RONALD WEBSTER. 

